June 11th, 2012:

We’ve created a new internal DNSBL “cidr.dnsbl.rollernet.local” that contains networks that have spammed us directly, contain abusive mail hosts, or providers that are sources of such.

This is not a new feature, other than making it available as a DNSBL. For many years this list of blocked networks has been maintained internally and we handled whitelisting requests on a per-customer basis. By moving it to a DNSBL you will now see entries in the mail logs, can opt to omit it from the DNSBL config, and add whitelist entries online. Additionally, anyone not using the DNSBL feature but is using SpamAssassin will now have access to it through the “ROLLERNET_CIDR” test.

The disadvantage of moving to a DNSBL is that anyone with the DNSBL feature disabled (or aren’t using the default list) may start seeing spam from these networks that were previously directly blocked by the internal list. We recommend enabling DNSBL and configuring “cidr.dnsbl.rollernet.local” to return to the previous behavior.

Networks are added through direct observation (or brought to our attention) and correspond to “whois” or RIR boundaries. Once added to the list entries are generally never removed unless the network owner requests removal and we can verify in our logs that the listed network is now clean.